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CHEMISTRY · Stage 9 · Chapter 13: Planet Earth and Continental Drift

Chemistry Stage 9 Comprehensive Review

5 min read 6 parts Lesson 5 of 5

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Stage 9 Comprehensive Review — Alhussan International Academy — Chemistry (Stages 7–9) notes: Revise atomic structure, bonding, reaction types, rates and Earth science from Stage 9.Sodium — an atom is 2,8,1 and loses one electron to form Na+ (2,8).Sodium ion size — the ion is sma…

  • Chloride ion size
  • Ion formation
  • Ionic compounds
  • Simple molecular substances
  • Giant covalent structures
  • Balanced equations

Section 1 of 6Atoms and ions

  • Sodium
    • an atom is 2,8,1 and loses one electron to form Na+ (2,8).
  • Sodium ion size
    • the ion is smaller than the atom because the outer shell has been lost, so the remaining electrons are pulled in more strongly by the nucleus.
  • Chloride ion size
    • it is larger than a chlorine atom because adding an electron increases repulsion.
  • Ion formation
    • metals form positive ions, and non-metals form negative ions or share electrons in covalent bonds.

Section 2 of 6Structure and properties

  • Ionic compounds
    • giant lattices with high melting points.
  • Simple molecular substances
    • low melting points.
  • Giant covalent structures
    • very high melting points.

Section 3 of 6Reactions and salts

  • Balanced equations
    • balanced symbol equations show conservation of atoms, for example 2Mg + O2 → 2MgO.
  • Making salts
    • salts are made from acids with metals, oxides or carbonates, followed by filtration and crystallisation.
  • Reactivity
    • it decides displacement and extraction methods.

Section 4 of 6Rates of reaction

  • Factors
    • rate increases with higher concentration, temperature and surface area, because collisions become more frequent and, for temperature, more energetic.
  • Investigating concentration
    • change only the concentration, measure gas volume or time, and control temperature, mass and surface area of the metal.
TopicKey phrase
IonicStrong electrostatic forces between ions
RateMore frequent effective collisions
DriftFossil and rock matches across oceans

Section 5 of 6Rusting investigation and graphs

  • Method
    • iron nails are placed in tubes exposed to air and water at different temperatures, and the time for rust to appear is measured.
  • Conditions
    • rusting needs both oxygen and water, and higher temperatures usually speed it up.
  • Graph
    • put temperature on the x-axis and time on the y-axis, label both with units, plot points accurately and draw a smooth curve.
  • Result
    • the time falls as temperature rises, so the rate of rusting increases.

Section 6 of 6Earth science

  • Wegener's hypothesis
    • continental drift is supported by matching fossils, rock strata and the fit of the continents.
  • Seafloor spreading
    • new crust forms at mid-ocean ridges and moves outward, shown by magnetic stripes.
  • Plate movement
    • plates move a few centimetres a year and build mountains where they collide.
  • Calculation
    • multiply speed by time: a plate moving at 2 cm per year travels 200 cm (2 m) in 100 years.
    • Use the data in the question, show working and write units.

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